Interactions of oxygen and CO with AgAu bimetallic nanoparticles on sputtered highly ordered pyrolytic graphite (HOPG) surfaces

Oxidation of AgAu bimetallic nanoparticles on sputtered HOPG by atomic oxygen and reduction of the oxidized surface by CO at room temperature were studied using X-ray photoelectron spectroscopy (XPS). For 2 nm-sized nanoparticles, prepared by postdeposition of Ag on Au-core, atomic oxygen exposure mostly leads to the formation of chemically inert oxygen species. This result is analogous to that of pure Ag and Au nanoparticles of similar sizes on the same substrate. In contrast, “Au on Ag-core” nanoparticles form chemically active oxygen species, suggesting that depending on detailed structures of bimetallic nanoparticles, diverse chemical properties can be obtained.